1. Field of the Invention
This invention relates generally to analyzing and eliminating the effects of signal to signal cross-coupling, and more particularly, to performing timing filtering and logic filtering to efficiently analyze and eliminate the effects of signal to signal cross-coupling.
2. Description of the Related Art
In electronic circuit applications, such as sub-micron and PC-board circuits, signal to signal cross-talk is a problem that is very difficult to control and overcome. Often, a capacitance develops between two or more signals, called cross-capacitance. Due to cross-capacitance, transitions in one signal can influence the behavior of other signals. A signal whose behavior is influenced by the signal transitions of another signal, is called the victim signal. A signal that influences another signal by means of cross-talk is called the attacker signal. During different periods of the circuit operation, an individual signal can be a victim signal at one point in time and an attacker signal at another point in time.
Attacker signals can cause victim signals to make: inadvertent transitions; transitions too early; or transitions too late. Any of these situations can cause serious errors in electronic circuits. One of the most serious problems faced by designers occurs when an attacker signal causes the victim signal to transition too early or too late. These problems are known as dynamic delay variations.
Dynamic delay variations can occur when the attacker signal switches in the same direction as that of the victim signal. This can cause the driver to switch the victim signal too early because the victim signal is already being switched, at least partially, by the attacker signal. Similarly, when the attacker signal switches in the opposite direction, the driver could switch the victim signal too late because it has to remove additional charge that was placed there by the attacker signal. These slow-down and speed-up dynamic delay variations can cause serious errors in the performance of the electronic circuit.
To date, the primary method of addressing cross talk problems has been primarily a trial and error approach. Currently, there are no automated methods to address the dynamic delay variation problems that are caused by cross-coupling signals. Generally, designers are reduced to predicting where cross-coupling may occur or only addressing the signals that are actually known to have cross-coupling tendencies, such as signal busses, which are generally known to have high coupling capacitance between adjacent bits, and very similar timing patterns. The process of identifying and addressing the problems of cross-coupling induced dynamic delay variations with today's methods are, at best, guesswork, and they are inefficient.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.